The formation of vials from short lengths of glass tubing is a well known manufacturing practice. Obviously, to convert a length of glass tubing into a vial, the one end of the tubing must be closed, generally in a semi-spherical shape and the other open end must be shaped so as to provide sealing surfaces for a closure or stopper. The most common form of closure for a vial is now fabricated by injection molding of a thermoformed plastic. Such closures are formed to relatively precise dimensions and it necessarily follows that for the closure to properly function, the open or finish end of the vial must be similarly formed to accurate dimensions. Thus, the bore of the vial neck should define a true cylindrical surface of accurate diameter. Moreover, the flanges provided on the external surfaces of the vial neck for retaining a closure thereon must be similarly accurately formed.
The tools heretofore employed for finishing the interior and exterior surfaces of the neck flanges of the vial have not been found capable of maintaining a high degree of forming accuracy as the speed of forming the vials and the length of production runs have been gradually increased over the years. One such existing system for forming the open end of a glass vial is that disclosed in U.S. Pat. No. 2,952,943 to Zauner. The mechanism employed in the Zauner patent effects reasonably reliable tooling of the internal diameter of the vial neck opening, as was required when vials were primarily closed by insertion of stoppers. The accurate formation, however, of an external shoulder on the periphery of the vial by the mechanism disclosed in the Zauner patent was not possible because such mechanism merely constituted a stationary anvil over which the neck portions of the vial were rolled during the forming operation on the interior surfaces. Such an arrangement obviously was not capable of producing an accurately dimensioned external shoulder on the vial finish.
A later form of commercially operated machine is disclosed in Lewis U.S. Pat. No. 3,343,937. In this patent, a mandrel is inserted in the heated mouth portion of the vial and the external surfaces of the vial are formed by two cooperating, rotating rollers which are brought into engagement with the top and bottom sides of the heated vial end and rotated to form threads or shoulders on the external periphery of the vial neck. The cooperating rollers are mounted on a pair of medially pivoted arms and the other ends of the arms are biased toward the desired final tooling position by a common spring mounted on a shaft carrying a pair of stop members which define the limiting inward movement of the tooling rollers. This mechanism works satisfactorily if the axis of the vial being operated on is precisely aligned with the center line between the two tooling rollers, but if the vial is misaligned slightly, the mechanism is incapable of adjusting the position of the tooling rollers to accommodate such misalignment, without imposing a greater force on one of the rollers, hence inaccuracy in the forming of the threads or projections on the vial end necessarily resulted. Differential heat expansion of the roller supports will also produce lateral misalignments of the forming tools.